Is the London 2012 Olympics countdown clock correct?

With a great fanfare on March 14th, the London 2012 Olympic Games organisers unveiled a clock counting down to the start of the games.  The clock was supplied by Omega, who have been official timekeepers at the Olympics for 25 years, so they know their stuff, or do they? As I watched the countdown, I noticed something strange. It went something like this:

Days - Hours:Mins:Secs
500 - 00:00:03
500 - 00:00:02
500 - 00:00:01
500 - 00:00:00
500 - 23:59:59
500 - 23:59:58
500 - 23:59:57

The clock counted down to midnight when it got to 500 - 00:0:00 and rolled round to the next day, 500 days to the Olympics!

Now, am I being dense here? Surely 500-days-and-one-second "to go" is less than 500-days-23-hours-59-minutes-59-seconds "to go".  500 days is 499 days and 24 hours, so anything LESS than 500 days isn't 500 days plus some hours. Shouldn't the number of days decremented when the hours, minutes and seconds went through zero?  I would have expected this:

Days - Hours:Mins:Secs

500 - 00:00:03
500 - 00:00:02
500 - 00:00:01
500 - 00:00:00
499 - 23:59:59
499 - 23:59:58
499 - 23:59:57

So how many days left should be shown on the clock now? The number on display, or one less than that?
What do you think?
Links:
London 2012 official news about the unveiling of the countdown clock

News report on the breakdown of the countdown clock the day after it was unveiled

Daily Telegraph's daily countdown to the London 2012 Olympics